Christopher Currey University of Minnesota Graduate Student
Moth orchids (genus Phalaenopsis) have been taking the potted plant world by storm for the last decade. They are now second only in total sale value to poinsettias, yet per pot they are the most valuable crop on the market today. The advent of advanced tissue culture and production methods has brought the plant out of the elite Victorian glasshouse to the shelves of nearly every retailer, allowing them to become the most accessible orchid on the market today. Combine this accessibility with their ease of growing in the home environment and you have a wonderful, rewarding tropical orchid for the everyday home gardener.
Photo 1: Phalaenopsis orchids are a commonly sold in box stores to upper scale garden centers. David Zlesak
Name, nomenclature, etymology
The genus Phalaenopsis received its name in 1825 from the Dutch botanist Blume. The common name, the moth orchid, reflects the Greek etymology behind the scientific name: phaluna, moth, and -opsis, resembling. This is in reference to the moth-like blossoms produced on long spikes. There are currently 63 distinct species, with numerous subspecies and hybrids found in nature, not to mention the countless crosses made by hobbyists and professionals world wide.
Phalaenopsis plants are fairly easy to identify when in bloom. Flowers in the genus have a broad diversity in color among the species, with smaller variation in shape. There white and pink flowers that resemble the commercial varieties seen most often, yet there are also yellows, purples and even some green ones that are solid or decorated with stripes or bands. The distinct inflorescence is comprised of flowers borne in numbers from few to many on a stem arising from a leaf axil. In fact, when a flower stem first starts to appear, it is difficult to distinguish it from the roots of the plant, which also arise from leaf axils.
Photo 2: The flowers of Phalaenopsis orchids is reminiscent of moths. David Zlesak
The roots are another distinguishing part of the plant. Thick green or purplish roots with a spongy white coating often protrude out of the pot and grow in the air. It is quite common for people to be worried about this when they initially start growing the plants and see these roots produced! The roots are perfectly fine growing outside the pot like this, as it is part of their natural plant habit. In their native environments Phalaenopsis plants are either epiphytes or, less commonly, lithophytes growing on plants or rocks, respectively. These roots grow out and act as anchors and attach to other plant material or rocks, while absorbing moisture and nutrients in addition to acting as photosynthetic organs!
Finally, although the leaves of these plants may not seem as attractive as the flowers, they can serve as an attractive foliage plant when out of bloom. Most species and commercial varieties in the genus have an average of five or six leaves from six to twelve inches in length and around four or five inches wide. The leaves are often shiny or leathery in appearance and plain green or purple with some white mottling. One aspect of the plant that is worth noting is the lack of pseudobulbs that many other orchids have. For this reason, Phalaenopsis were particularly prized in the 1800’s. When ships would cross oceans filled with plant material bound for Europe, plants with pseudobulbs would have greater success upon reaching their destination, while moth orchids had no storage organs and would not ship as well until advances in shipping technology were made.
Photo 3: Although the flowers are typically prized more than the foliage, the foliage can be quite attractive. David Zlesak
Native Environment (geographic/environment)
Phalaenopsis is a genus of from tropical regions in the Old World. The range is throughout tropical Asia east to the Philippines and west to Sri Lanka. In these tropical regions the plants grow in habitats that experience either seasonal drought, seasonal periods of cooler temperatures, or constant moisture/humidity. This is one reason that the plants are quite versatile and suitable for growing in the home, as these environments are easy to recreate by combining natural changes in the season and cultural practices.
Culture and Environment
When potting moth orchids, the choices of different potting media can be staggering. There are numerous commercially-offered media, and the number of “recipes” for custom-mixed media rivals the number of dubious remedies some popular authors have for keeping plants healthy. In reality, Phalaenopsis are quite amenable to any growing medium, as long as cultural conditions are adjusted to suit the medium. I have even heard anecdotes of people growing moth orchids in shredded tires and socks! The two most common media for moth orchids are long grain Sphagnum moss or a standard bark-based mix containing bark, charcoal, peat, and perlite. When potting with a bark-based mix place the bare-root plant in the container, fill in and around the roots with the mix and press the medium in firmly around the roots. When using sphagnum, loosely place the moss around the roots while not packing or compressing the fibers.
Photo 4: This porous product gaining in popularity as an orchid medium is a form of baked clay. David Zlesak
A variety of containers may be used for potting Phalaenopsis orchids. A true classic, unglazed terra cotta or clay pots have been used many decades. Benefits include increased aeration and weight, causing increased gas exchange and a heavy base to support the plants, respectively. Drawbacks are an increase in salt accumulation, difficulty in sanitization and breakage. More commonly used today, plastic pots are perfectly suitable for orchids. While they are lighter and are not as porous, they are easier to sanitize and reuse and do not accumulate excess salts from water or fertilizers. One aspect to take into consideration when selecting plastic pots is the color. As mentioned earlier, Phalaenopsis roots may absorb water and nutrients, but they will not do this unless they are in contact with the potting medium. When clear plastic pots are used, more roots grow down into the medium, whereas when pots are used that do not transmit light the number of aerial roots will increase.
Photo 5: Moth orchids come in many colors and color combinations. David Zlesak
An alternative to potting, some species of Phalaenopsis with pendant inflorescences are well-suited to mounting. This may is easily done by taking a slab of tree fern or cork that has been sterilized and a layer of damp long-grain sphagnum moss on it below where the plant will be placed. Next, place a bare-root plant on top of the sphagnum topped with another thinner layer of moss. Finally, tie the plants and moss down to the mounting material using fishing line. This provides an attractive alternative to potting. However, care must be taken with these plants to not let them dry out. They will need more frequent watering as there is not much media to hold moisture over a longer period of time.
Moth orchids vary in their feeding requirements. When growing species you may feed at every watering using 1/4-1/2 teaspoon of a balanced water soluble fertilizer per gallon of water applied during the active growing season. Feeding frequency and strength may be decreased to every other or every third watering with a maximum of 1/4 teaspoon fertilizer per gallon of water applied during the winter months when vegetative growth will not be as vigorous. Alternatively, the commercial hybrids may be grown with more feeding year-round without a seasonal break under optimum light and other growth conditions. Using 3/4 - 1 teaspoon of a balanced water soluble fertilizer per gallon of water applied is recommended for hybrids growing under more optimal conditions, combined with a clear-water leaching every fourth watering.
Photo 6: Careful pruning of flower spikes can encourage side branches and additional flowers. David Zlesak
Phalaenopsis grow fine in the temperature range experienced in the home environment. Temperatures ranging from the lower 60’s to the higher 70’sF are suitable for growing these plants. The air temperature is also key for initiating flower production. Maintaining the day and night temperatures below 80°F (preferably in the 60’s) for three or more weeks will allow flower initiation to commence. This can be easily done by having the plant placed next to a window during the winter where the temperature may be cooler than the rest of the room. After a while you will see the beginning of an inflorescence coming out of one or more of the leaf axils. This will take a while to develop, yet it will be well worth the wait. A single flower on a moth orchid may last around a month, so a stem with multiple blossoms may be blooming for months! When the plant has finished blooming, do not be in a hurry to chop the stem back. Wait a few weeks and cut the stem back about a half inch above where it turns from green (live) to brown (dead). This will result in branching and more flowers, quite an impressive sight.
Light levels suitable for growing Phalaenopsis ranges from 1,000-3,000 foot candles. You can achieve these levels in the home by growing plants in north, east or shaded west windows. In the summer, plants may be placed outdoors underneath lathe or shade from trees.